The present invention relates to a recoil damping device for portable firearms.
As is known, the stock of rifles has the purpose of fixing the distance between the shooter's shoulder and the trigger, of taking part in defining the center of gravity of the firearm and of distributing the pressure generated by the recoil force over a larger surface, so as to reduce the unit value and transmit it to the shooter's shoulder.
In order to reduce the dynamic load on the shoulder, caused by the recoil of the firearm, or to improve its ballistic characteristics, numerous devices have been proposed, including accessories to be applied to the stock and internal mechanisms of various kinds.
Damping systems are known, for example, that are constituted by an elastic portion formed in the rear part of the stock and adapted to partially absorb the recoil energy by deforming.
An important drawback of that type of system is that the elastic portion deforms, during the recoil step, and easily causes lateral shifting in the rearward motion of the rifle. Therefore, the motion of the recoiling firearm does not follow the longitudinal axis thereof but is diverted, with consequent loss of the aiming line and of the correct firearm placement by the shooter.
Another conventional damping system is substantially constituted by a butt plate that is mounted on the stock of the rifle, by interposing damping means generally constituted by helical springs.
GB2371104 and EP1657518 disclose systems of that type.
Namely, EP 1657518 discloses a recoil damping device that includes an insert, arranged in the stock of a rifle, and a damping means constituted by helical springs and dampers. Such device includes a movable interface that retains the damping means and is provided with stems that can slide within guides provided in the insert. The movable interface is made of plastic material that is adapted to deform, when needed, during recoil, in order to keep the rifle true, ensuring at the same time the coaxial arrangement of the stems that slide within the guides.
The damping device known from EP1657518 is effective in damping the recoil force and reduces the shifting of the rifle during shooting, without amplifying the negative effects of an incorrect firearm placement. However, such system is constructively complicated and therefore productively expensive and relatively heavy.
U.S. Pat. No. 7,926,216 discloses a damping device constituted by a piston that is integral with the butt and is adapted to move in a seat in the stock of the firearm, in contrast with a helical spring, which works by traction by virtue of a lever system. The system described in U.S. Pat. No. 7,926,216 is constructively complicated and heavy.
U.S. Pat. No. 6,684,547 discloses a recoil damping system constituted by a set of elastic members that are interposed with rigid members that are mounted on a stem that can slide between the stock of the firearm and the frame.
Another type of damping system, used in long firearms, is constituted by a stock that includes cavities provided in the comb of the stock and filled with material adapted to absorb energy.
EP1348928 describes a stock of such type, which reduces the dynamic load on the shooter's shoulder, caused by the recoil of the firearm, at the same time allowing to improve the ballistic behavior of the firearm, reducing barrel rise at the muzzle, at the moment of firing, with consequent speed of target acquisition for shots after the first one.
The damping system described in EP1348928 allows a reduction in the dynamic load caused by recoil, which is particularly advantageous in the case of use of high-pressure and high-weight cartridges.
U.S. Pat. No. 2,767,500 discloses a shock absorption mechanism having an elliptical spring and a cylinder filled with hydraulic fluid.
DE2305562 discloses a shoulder pad provided with shock absorber means constituted by rubber pins of different length and elasticity.
In general, the above described prior art systems, based on mechanisms that are internal to the stock, have the drawback of being structurally complicated and therefore expensive.
The accessories to be applied to the stock can have a lower cost but do not offer optimal functional characteristics.
Also, in the prior art systems, the behavior of the elastic means is linear, i.e., the flexibility of the helical springs and of the other elastic members used is approximately constant. In practice, the deformation of the elastic members is directly proportional to the applied compression force, thus generating a linear chart on the Cartesian plane. This entails that the damping system is effective for a narrow range of munitions. In practice, the system works well only for certain munitions but is far less effective for more powerful or weaker munitions.
In other words, in the case of much more powerful munitions, the traditional damper deforms excessively and fully collapses, transmitting a considerable impact force to the shooter's shoulder. In the case of much weaker munitions, instead, the system does not deform sufficiently and does not reduce the effects of recoil.